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QJRAY S(LVER 10A ES <br /> 8. In verbal discussions prior to the submission of TR-12, a faulty drill rig was initially suspected <br /> to be the source of the contamination of GW-4. What measures will be taken to minimize the <br /> chance of contamination when constructing the proposed GW-4R. <br /> Prior to understanding the historic machine shop activity associated with the area, initial <br /> discussions focused on the possibility a faulty drill rig had released a small amount of organics. <br /> When attempts to purge the well were unsuccessful, OSMI came to believe a larger amount of <br /> organics were present and began researching other possible causes as a large volume organics <br /> being accidentally spilled into the well bore was unlikely. For future monitoring well drilling <br /> OSMI will ensure the driller is experienced with monitoring wells and the well drilling will be <br /> observed by environmental staff or consultants for irregularities. None-the-less, as discussed in <br /> items 3 through 7, OSMI withdraws the proposal for GW-4R. <br /> 9. Commit to adding an initial complete hydrocarbon analytical suite to GW-4R once completed. <br /> And if results indicate hydrocarbons continue to sample for those constituents quarterly. <br /> As discussed in the responses to items 3 through 8, OSMI no longer proposes a replacement well <br /> G W-4R. <br /> 10. Section 4.1 Characterization and Monitoring Plan Implementation states that OSMI's <br /> voluntary effort may include three conditions to further characterize the pollutant. Also, verbal <br /> discussions indicated a third party consultant would be retained to complete the characterization <br /> of the contaminant. Please commit to and provide the Division with a detailed plan and <br /> estimated time of completion for a complete characterization of the contaminant sufficient <br /> enough to identify the source, extent, composition and potential impacts of the contaminant <br /> discovered in GW-4. <br /> OSMI Contracted Geosyntec, see recommendations in Attachment 5. <br /> 11. Given that DRO's were detected in SW-22 will additional upgradeint and downgradient <br /> sampling for DRO's be conducted as part of the characterization to be completed by a third <br /> party consultant, if so please indicate which locations will be sampled? <br /> No additional sampling for DRO is proposed in Sneffels Creek, as DRO is not a regulated <br /> constituent, no sheen has been observed, and analytical results suggest a lack of regulated <br /> constituents in the groundwater organics. <br /> 12. SW-22 has been selected for a temporary surface water sampling point. Will this become a <br /> permanent surface sampling point moving forward? <br /> While OSMI has an interest in monitoring at SW-22, it is not being proposed as a permanent <br /> station at this time. <br /> 4 1 P a g e <br />